resolv.conf is used by Linux servers for specifying DNS servers used to domain name resolution.

Location of the file is

/etc/resolv.conf

Example

root@maps:~# cat /etc/resolv.conf 
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.8.8
root@maps:~# 

In above example, google public name servers 8.8.8.8 will be used for DNS resolution.

If you edit this file, it get reset every time your reboot.

Editing resolv.conf on CentOS

On CentOS/RHEL, you can directly edit /etc/resolv.conf, it won’t get overwritten

vi /etc/resolv.conf

Editing resolv.conf on Ubuntu/Debian

If you need to set DNS resolver, you need to edit file

vi /etc/resolvconf/resolv.conf.d/base

Add

nameserver 8.8.8.8

One liner

echo "nameserver 8.8.8.8" > /etc/resolvconf/resolv.conf.d/base